function lazyload(){
        var temp1 = window.innerHeight || document.documentElement.clientHeight
        var temp2 = document.body.scrollTop ||document.documentElement.scrollTop
        var totalHeight = temp1 +temp2
        var imgsObj = document.querySelectorAll('img')
        imgsObj.forEach(function(item,index){
            if(item.offsetTop<totalHeight){
                item.src = item.getAttribute('src-real')
            }
        })
    }
    lazyload()
    window.onscroll = lazyload
